What Happens When a Crew Hits Rock
What is under an Edmond yard
Red clay on top, and then it varies by neighborhood and sometimes by property line. Sandstone and shale sit close to the surface across a good deal of the area, and in the older parts of town you will also find hardpan, chunks of the previous fence's footings, driveway spoil that a builder buried in 1978, and the occasional slab of the porch that used to be there. Any of it will stop an auger.
What refusal actually looks like
The bit stops advancing and the machine starts wanting to climb out of the hole instead. On a two man auger, the operator feels it immediately. On a skid mounted unit, the giveaway is the hole going from a two minute job to a fifteen minute one. Genuine refusal is not the same as a dull or wrong bit, and it is worth asking which one you are looking at, because a crew that has been running the same worn teeth all week will hit rock more often than the geology explains.
The ways out, cheapest first
- Move the post. Shifting a hole eight or ten inches along the line often clears the obstruction entirely and costs nothing but a slightly uneven bay.
- Rock auger or a carbide toothed bit, which handles softer shale and weathered sandstone without special equipment.
- Hand work with a breaker or a rock bar, slow but reliable on a single stubborn hole.
- A hydraulic breaker on the machine, which is a rental line and shows up as a real cost.
- Core drilling and epoxy setting the post into solid rock, used when the obstruction is a buried slab rather than something to be broken up.
How the cost should be handled
Three arrangements are common, and all three are fine as long as one of them is written down before the first hole. A per hole rock charge, quoted in the contract, so the number is known. An hourly rate for breaking, with the crew logging the time. Or an allowance built into the price, a set figure that covers a stated number of difficult holes, refunded if unused. What you do not want is silence, because silence turns into a verbal estimate delivered while your yard is torn open.
The opposite problem
Not every hard hole is rock. In newer additions the trouble is often loose engineered fill, which augers beautifully and then holds a post about as well as a bucket of sand. That situation calls for a deeper or wider hole and more concrete, and it costs money in exactly the same way. Ask how the crew handles both ends of that range, because a fence line can easily run through shale at one corner and soft fill at the other.